1. In 1869, the first transcontinental railroad was completed in California with the driving of the golden spike in Promontory Summit, Utah. This event was significant in California history as it marked the end of a long journey that had begun in Sacramento in 1863, and it made cross-country travel faster and easier.

2. In 1969, the infamous Manson Family murders took place in Beverly Hills. This horrific event shocked the nation and has since gained infamy as a significant instance of the dark side of California's counterculture movement in the late 1960s.

3. On August 10, 1913, the Los Angeles Aqueduct was completed, providing the city with a new source of freshwater from Owens Valley in the Sierra Nevada mountains. This engineering feat was essential in the development of Los Angeles as a major metropolitan area, and it also had a significant impact on the natural environment and communities that depended on the Owens Valley's water.

4. The 1984 Summer Olympics opened in Los Angeles on August 10, 1984. This marked the second time the city had hosted the games, and it was a significant event in California's history as it showcased the state's diverse culture and natural beauty to the world.

5. In 1964, the Watts Riots started on this day in Los Angeles. The occasion marked a significant moment in California history as it exposed the racial tensions and police brutality against African Americans in the city and sparked nationwide conversations about civil rights and social justice.